Hyponatremia clinical presentation ddx

A 65-year-old female presents with nausea, headache, and confusion. Laboratories reveal a serum sodium of 128 mEq/L. Brain imaging is unremarkable. Which of the following is the most likely cause of her hyponatremia?

1: Severe hyperglycemia
2: IV mannitol administration
3: Primary adrenal insufficiency
4: Overzealous water drinking